When buying or choosing a mattress, there is currently little information to guide the user, in terms of selecting a mattress that will suit his/her particular body characteristics. Mattresses are presented as a general range from basic quality to high quality, with no account taken of the particular physique of the user, and no attempt to match mattress characteristics to the physical characteristics of the user. This contrasts sharply with, for example, the selection process for shoes where the selection process involves taking into account the physical characteristics of the user including foot length, width, and arch height are taken into account when selecting the shoe, and shoes are categorised according to the relevant parameters.
Recent research (Bain 1997 Phd Thesis, University of Surrey) has indicated that certain relationships exist between user physique and optimal mattress characteristics. For example, to maintain spinal alignment when lying on the side (generally recognised as desirable to prevent back pain) the optimal firmness of the mattress depends on the breadth from the saggital plane of bony prominences such as the greater trochanter and ilium, and on the body mass distribution of the user. The mattress needs to provide the correct amount of resistance to allow these bony prominences to displace into the mattress the correct distance to preserve a straight spine. The amount of resistance required depends on the user parameters mentioned.
When lying on the back, it is generally recognised that the natural curvature of the spine, including a lumbar curve, a thoracis curve, and a cervical curve, should be maintained for comfort. Once again, it has been shown that the optimal characteristics of the mattress to maintain these curves depends on the individual user shape. For example, a user with a tighter (smaller radius) lumbar curve may require a mattress with greater differential yield between adjacent regions of the mattress. This has implications, not only for the firmness of the mattress, but also in the spatial resolution (e.g. springs per square meter, or foam profile density) of the support, and the tensile properties of the top layers of padding. A mattress that is soft overall, but has a very coarse distribution of springs, or a stiff, hammock-like cover, will not be able to accommodate a tightly accentuated lumbar curve.
Some steps have been taken previously in an attempt to provide information relating to the individual user that may be used to inform the choice of mattress.
One example is pressure mapping. In this method, a pressure mapping device, consisting of a two-dimensional array of pressure sensors, is used to display a two-dimensional map of the pressure distribution on the skin of the user when lying on the mattress. Nominally, certain parameters in the mattress may be modified to optimise the pressure distribution. This method has a number of problems. One problem is that it is not well understood what would constitute a good or bad pressure distribution, in terms of maintaining a good posture. Current understanding and interpretation of pressure maps is focused predominantly on the issue of pressure ulcers in hospital patients and so is more concerned with locating areas of high pressure which may lead to poor skin perfusion. Strategies for adjusting inflation pressures to minimise peak pressure values may be effective in maintaining skin health but will be of little value for maintaining good sleeping posture.
Furthermore, pressure mapping technologies are expensive, and the expense may be prohibitive in many retail establishments. A great deal of specialist scientific expertise is also required to maintain, calibrate, and operate pressure mapping systems in such a way as to obtain valid results. This level of expertise is very unlikely to be on hand in a retail context.
More recently (Bain, Hubbard, Woolfson) a system was developed for capturing a basic, simplified shape of the body. This shape could then be used alongside historical data relating body shape to mattress preferences. This system is published in United States patent specification no. US 2011/0009776.
However, this system also exhibited certain limitations. The 3 dimensional shape of the body was not captured. Information about the body type was only inferred from 2-dimensional silhouettes in front view and side view, and therefore relied on some broad assumptions, and could only broadly categorise body types.
Furthermore, the capture of the body shape in the standing position was considered by some skilled in this area, to be unrepresentative of the body shape while lying down, although it was also widely acknowledged that the shape captured while lying down would represent a non-ideal condition, with the body posture already distorted.